1. Field of the Invention
The present invention relates to a rotary damper device, and more particularly to a rotary damper device that is used in a rotational cover or a rotational door.
2. Description of the Related Art
A conventional rotary damper device is generally constituted in such a manner that a rotor shaft mounted with a check valve is enclosed in a case in which oil is filled, and a cover is tightly fitted and fixed to the case by screws, supersonic wave welding or the like. Such a rotary oil damper device is used not only in a rotational cover or a rotational door but also as a damper device regulating the rotating or swinging speed of a toilet seat and/or a seat lid. When the toilet seat/seat lid with the damper device is moved in a closing direction from an opened state, a rotor shaft rotates with the toilet seat to make a check valve mounted to the rotor shaft tightly contact with a vane of the rotor shaft. The vane is provided with an orifice, which is closed by the check valve abutting against the vane to restrict the flow of oil, and thus, the toilet seat/seat lid is slowly closed.
When the toilet seat/seat lid is moved in an open direction from the closed state, the rotor shaft is rotated or swung, and the check valve attached to the rotor shaft is released from the contacting state with the vane. As a result, the orifice formed in the vane is opened so that the oil can move without resistance and the toilet seat/seat lid can be easily opened.
However, check valves in the prior-art have various problems that need to be solved. For example, a conventional check valve is formed substantially U-shaped and is movable until the right or left butting part of the check valve abuts against the vane. In this type of check valve, since the check valve can move in either direction by oil resistance as the rotor shaft moves, it requires some time for the check valve to close the orifice of the vane. This period causes a slip angle that does not work as a damper function for the rotor shaft. In the case of the slip angle being large, when a toilet seat is opened halfway and released, the toilet seat may collide with the toilet stool bowl. Also, the large slip angle causes variations in angle when the toilet seat is braked.
A damper device without a backlash, is complicated and requires a lot of components. Also, a rotary damper is a damper in which the slip angle is reduced by using a spring, hut many components are required and its assembling workability is not satisfactory.
A device in which a viscous fluid pressure receiving part is provided with elasticity is also known in the prior art. However, with this device, the elastic deformation part is formed in the portion to which a high pressure of viscous fluid is applied causes a problem of its durability.